ADU Builders
Orange County
We only build ADUs. One contract covers custom 3D design, in-house municipal permits across all 34 OC cities, and ground-up turnkey construction.
ADU Services from an
Orange County Design-Build Team
From feasibility through final inspection, one dedicated contractor handles your full scope so timelines and construction quality stay clear.
ADU Plans & Architectural Design
Work directly with dedicated ADU architects who understand Orange County municipal zoning. We craft site-specific 3D floor plans, structural engineering calculations, and Title 24 energy compliance sets that maximize your usable yard space and property value.
ADU Permits & City Approvals
Our in-house permit team submits directly to your local building department (Irvine, Newport Beach, Anaheim, Santa Ana, Costa Mesa, etc.). We manage all plan check reviews, city comments, and correction notices until your building permit is fully issued.
Detached ADU Construction
Build a private, standalone dwelling in your backyard. From compact 350 sq ft studios to spacious 1,200 sq ft 2-bedroom luxury residences, our licensed craftsmen handle excavation, foundation, framing, plumbing, electrical, and turnkey luxury finishes.
Garage to ADU Conversion
Convert your underutilized 2-car garage into a legal, permitted 1-bedroom or studio living space. Because the existing foundation and framing are utilized, garage conversions offer the fastest timeline and highest cost efficiency in Orange County.
Junior ADU (JADU) & Attached Extensions
Create a compliant Junior ADU (up to 500 sq ft) within your existing home footprint or build an attached suite extension. Ideal for aging parents, college students, or private guest quarters with lower upfront construction investment.
Find your ADU
The Balboa Studio
From $149,000 • 350 sq ft
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The Laguna Suite
From $159,500 • 430 sq ft
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The Monarch One
From $182,000 • 560 sq ft
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The Pacifica Two
From $208,000 • 715 sq ft
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The Catalina Grand
From $242,000 • 800 sq ft
Configure →Living & Interiors
Every unit is designed to feel like home from day one. Warm finishes, smart layouts, and natural light throughout.
Open living, seamlessly connected
Living room, kitchen, and dining flow together in one bright, airy space with custom cabinetry.
Bedrooms that feel like a retreat
Vaulted wood ceilings, warm natural light, and integrated storage designed for calm rest.
Chef kitchens & quartz countertops
Full-size stainless appliances, soft-close custom cabinetry, and durable solid surface counters.
Built for California
Fire-resistant, climate-ready, and solar-compatible infrastructure engineered for Orange County climate and code.
All Electric
Ultra-efficient ductless heating & AC.
Steel Frame
Precision engineered structural steel framing.
Fire Ready
Class-A fire-resistant exterior cladding & roof.
Solar Ready
Prewired for solar integration & battery storage.
ADU Projects Built Across
Orange County
See how our dedicated team handles real Orange County lots, city plan check timelines, and fixed budgets throughout the county.
AFTER
BEFOREThe Newport Coastal Studio Transformation
Newport Beach, CA • 420 sq ft
A cluttered detached 2-car garage converted into a bright, contemporary guest suite with vaulted ceilings, custom oak cabinetry, and full in-unit laundry.
AFTER
BEFOREThe Irvine Modern Detached Two-Bedroom
Irvine, CA (Woodbridge) • 715 sq ft
Ground-up custom detached 2-bedroom ADU featuring floor-to-ceiling sliding glass doors, mini-split climate control, and a private landscaped patio.
From Site Visit to Keys in
6 to 9 months.
Other builders hand you off between independent designers, permit expediters, and contractors. ADU Alliance coordinates all four inside a single transparent project plan with zero rejected permits.
Property Feasibility
Lot setback analysis, sewer/water/electrical mapping, HOA rule review, and fixed scope proposal.
Architectural Design
3D modeling, floor plans, structural engineering calculations, and Title 24 energy compliance sets.
City Permitting
Plan check submission, city comment resolution, and guaranteed permit issuance across Orange County.
Turnkey Construction
Licensed Class B ground-up construction, weekly photo updates, final inspection, and keys handover.
Watch your ADU come to life
Your personal homeowner dashboard tracks every milestone from initial survey to move-in day with live city plan check logs and weekly job-site photo reports.
Four Ways to Step In
Pick the exact path that fits where you are today - whether exploring initial zoning, ready to walk your lot, or requesting an architectural quote.
On-Premise Lot Walk
Free 30-Minute Property Feasibility
An ADU specialist walks your Orange County property, checks setbacks, sewer depth, and maps out your options on the spot.
Video Consultation
Zoom with a Senior Planner
Share your property screen on Zoom. Get instant setback readouts, 3D model recommendations, and budget ranges.
Phone Consultation
15-Minute Expert Q&A
Prefer to talk? Call our Irvine planning desk directly for immediate answers on costs, city permits, and timelines.
2026 OC ADU Guide
28-Page Comprehensive PDF
Line-item cost tables, city permit timelines, floor plans, and zoning rules across all 34 Orange County cities.
The ADU Specialists
Orange County Homeowners Trust
As an experienced ADU contractor, we work with city reviewers, site constraints, and Title 24 code details every day so your project avoids common delays.
Licensed General Contractor (B)
ADU Alliance holds an active California General Contractor (B) license Verified CSLB Alliance with comprehensive general liability and workers compensation coverage.
200+ ADUs Completed in Southern California
Our portfolio spans detached backyard builds, garage conversions, JADUs, and attached extensions across every major Orange County municipality.
15+ Years ADU-Exclusive Focus
Many contractors treat ADUs as a side gig. We focus exclusively on ADU design, permitting, and construction every single day.
Transparent, Fixed-Price Contracts
We do not use open-ended billing or surprise change-orders. Each scope starts with clear, itemized pricing covering architecture, permits, and construction.
In-House Permit Management Across 34 Cities
We submit and manage permits directly with Irvine, Newport Beach, Anaheim, Santa Ana, Huntington Beach, and local building departments to prevent avoidable delays.
Single-Source Design-Build Accountability
One team, one contract, and one dedicated project manager from initial lot assessment through final city inspection and key handover.
Everything you need to know
Answers regarding zoning eligibility, prefab construction, permits, and financing.
Want to know what you can build on
your lot?
Tell us about your property. We confirm your ADU options, municipal setback allowances across Orange County, and share realistic budget ranges within 1 business day.